Technical information

6 – APPLICATIONS
Phase Control & Current Follower Starter
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6.2.2 Phase Control
When the Starter Type parameter is set to Phase Control, the MX is configured to operate as a phase controller / voltage follower.
This is an open loop control mode. The firing angles of the SCRs are directly controlled based on voltage or current applied to the
Analog Input. A reference-input value of 0% results in no output. A reference-input value of 100% results in full (100%) output
voltage. The actual voltage or current input that results in a given output can be adjusted through the use of the Analog Input Offset
and Analog Input Span parameters. The Phase Control mode has many uses. Two typical applications are use in master/slave starter
configurations and as a basic phase controller.
Phase Controller:
When in Phase Control mode, the MX can function as a general phase controller. Phase control can be used to directly control the
voltage applied to motors, resistive heaters, etc. When in Phase Control mode, the phase angle of the SCRs and hence the voltage
applied is directly controlled based on the measured analog input signal. The MX’s reference command can be generated from any
0-10V, 0-20mA, 4-20mA source such as a potentiometer, another MX, or an external controller such as a PLC.
The Phase control mode can only be used on continuous/fan cooled starters. The bypassed starter does not have the thermal capacity
to continuously operate at rated amps in phase control mode and the bypass contactor is not used. Use the RC power stack.
Master/Slave (Lead/Follower) Starter Configuration:
In the master / slave configuration, one “master” starter can directly control the output of one or more slave starters. To utilize the
master / slave configuration, one starter needs to be defined as the “master” starter. The Starter Type parameter of the “master”
starter should be configured appropriately as a Soft Starter (normal or ID), Phase Control, or Current Follower. If configured as a
soft starter, the acceleration and deceleration profiles need to be configured for proper operation.
The analog output of the “master” starter should be set to 0-100% firing and connected to the analog input(s) of the “slave” starter(s).
“Slaves” should have their Starter Type parameters set to Phase control.
Note: The power stack must be rated for continuous non-bypassed duty in order to operate properly in Phase Control mode.
6.2.3 Current Follower
When the Starter Type parameter is set to Current Follower, the MX is configured to operate as a Closed Loop current follower.
Current Follower mode can be used to control the current applied to motors, resistive heaters, etc. The Current Follower mode uses
the analog input to receive the desired current command and controls the SCRs to output the commanded current. The MX’s
reference command can be generated from any 0-10V, 0-20mA, 4-20mA source such as a potentiometer, another MX, or an external
controller such as a PLC. When a start command is given, the RUN programmed relay output energizes and the SCRs are gated on.
A reference-input value of 0% results in no output. A reference-input value of 100% results in a current output equal to the Motor
FLA paramter setting. The actual voltage or current input that results in a given output can be adjusted through the use of the Analog
Input Offset and Analog Input Span parameters.
Note: The power stack must be rated for continuous non-bypassed duty in order to operate in Current Follower mode.